A low‐loss ring UWB bandpass filter

In this article, a compact and low loss ring ultra‐wideband (UWB) bandpass filter (BPF) with an enlarged perturbation element is designed and implemented on FR4 substrate. This filter at center frequency f0 of 4.16 GHz has presented almost very good measured characteristics including the bandwidth of 3.04–5.27 GHz (3‐dB fractional bandwidth of 54%), a low insertion loss of 0.8 dB, a high passband selectivity due to two transmission zeros in the passband edges, and a low group delay varied between 0.1 and 0.6 ns. Experimental results of the fabricated filter show a good agreement with the predict results.